ABSTRACT

Subsurface drip irrigation (SDI) has a foot-hold on the irrigation technology scene in the Southern Texas High Plains. The area of SDI has been expanding acres at an increasing rate each year and the trend will likely continue for the next couple of years. Field experiments were conducted from 1999 through 2001 to improve water management of irrigation systems in a semi-arid, deficit-irrigated production region in the Southern High Plains of Texas. The research evaluated the effects of pre-plant irrigation in terms of cotton lint yield, water use efficiency, and cotton fiber quality using spray, LEPA, and SDI delivery methods in treatments limited to irrigation capacities of 0.1 and 0.2 in/d (Bordovsky and Porter, 2003). Experiments were conducted at the Texas Agricultural Experiment Station at Halfway, TX, on moderately permeable Olton loam (fine, mixed, thermic Aridic Paleustolls) soils with slopes of less than 0.1%. From this data, production functions were developed in which lint yield was a function of water availability (soil moisture, seasonal rainfall, and irrigation), and type of delivery system. Enterprise budgets were developed utilizing the estimated production functions. Projected per irrigated acre net returns for SDI and LEPA were comparable at $123 versus $126, respectively. It was estimated that SDI increased lint yields by 47 pounds per acre over LEPA for the given irrigation, seasonal rainfall, and soil moisture availability conditions assumed. More importantly, SDI increased cotton fiber quality, receiving a $0.02 per pound price premium over LEPA. However, the economics of SDI is field dependent and thus, each application of SDI should be evaluated separately when evaluating the economics of SDI versus LEPA.

The cost of SDI may increase sharply as the field becomes irregularly shaped or elongated. Many factors influence the cost of SDI and producers should consult a dealer with design software to get an accurate estimate of cost before comparing the system with a LEPA center pivot system. SDI requires a higher level of management than LEPA to achieve the higher lint yields and increased cotton fiber quality found in this analysis.